Blasting explosives



United States Patent BLASTING EXPLOSWES Samuel Henry Davidson, Largs, and George Percy Sillitto, West Kilbride, Scotland, assignors to Imperial Chemical Industries Limited, a corporation of Great Britain No Drawing. Application May. 5, 1952,

Serial No. 286,212

Claims priority, applicationCreat Britain July 3, 1951 8 Claims. .(Cl. sa -1 When such explosive compositions are detonated the gases produced will, if the mixture is'not oxygen positive, contain excessive quantities of carbon monoxide. On the other hand if such compositions are oxygen posi tive but contain an insufiicient quantity of nitroglycerine or the like to effect a complete reaction on detonation the explosive gases tend to contain acidic oxides of nitro: gen. When large charges are'fired in aconfined space such as in tunnelling operations, nitrogen oxides are released, which in the presence of moist air forms acids which persist in the form of fine droplets for some considerable time and the amounts present may be sufficient to affect the throat and eyes. It is possible by including elementary sulphur e. g. 2 per cent in such oxygen positive explosives, if at least 6 times its weight of sodium nitrate is also included to prevent a release of oxides of sulphur, to eliminate or reduce considerably the formation of these oxides of nitrogen with the result that work can begin within -20 minutes after the explosion. It is, however, no longer desirable to use sulphur in this way owing to the acute scarcity thereof and hence it has become desirable to find other methods of overcoming this disadvantage. Also the necessity for including sodium nitrate prevents the inclusion of increased amounts of ammonium nitrate to produce explosive compositions of correspondingly increased explosive power.

It has now been found that these disadvantages can be overcome by incorporating into explosive compositions of the aforesaid kind such a quantity of calcium sulphate that 100 parts of the resulting explosive contain not more than 5 parts by Weight thereof.

If desired urea can also be included in such amounts that 100 parts by weight of the resulting explosive contain from 0.5 to 5 parts by weight thereof.

According to the present invention therefore the proc- -eSs for the production of high power gelatine or semigelatine blasting compositions containing a high proportion of ammonium nitrate comprises incorporating such a quantity of calcium sulphate that 100 parts by weight of the resulting explosive composition contain not more than 5 parts by weight thereof.

If desired according to the process of the invention such a quantity of urea can also be incorporated that 100 parts by weight of the explosive composition contain from 0.5 to 5 parts by weight thereof.

High power gelatine or semi-gelatine blasting explosive compositions containing a high proportion of ammonium nitrate according to the invention are characterised in that they include not more than 5 parts by weight of calcium sulphate with or without from 0.5 to 5 parts 2,711,366 Patented June 21, 1955 by weight of urea per 100 parts by weight of explosive composition.

If amounts of calcium sulphate are used greater than 5 parts by weight per 100 parts of the explosive composition the power of the composition is perceptibly reduced. Amounts less than about 0.5 parts by weight do not produce sufiicient effect.

Preferably 100 parts by weight of the explosive composition contain in the absence of urea 4 parts by weight calcium sulphate.

If urea is included it is desirable that the amount should bekept as low as possible, as high quantities lead to the production of explosive compositions which are unduly hygroscopic and hence necessitate the taking of special precautions to prevent the access of moisture. A pre'e ferred explosive composition according to the invention which includes urea is one wherein 100 parts by weight of the explosive composition include 2 parts by weight of urea and 2 parts by weight of calcium sulphate.

Compositions according to the invention are illustrated by the following examples in which all parts are parts by weight.

Example 1 Parts :20 mixture of nitroglycerine and ethylene glycol dinitrate 25.5 Nitrocellulose 0.9 Orthonitrotoluol 4.0 Woodmeal 2.5 Ammonium nitrate 62.8 Calcium'sulphate(anhydrite) t 4.0

The weight strength of the gelatine composition is 85.0 per cent of blasting gelatine.

Example 2 Parts 80:20 mixture of nitroglycerine and ethylene glycol dinitrate 25.5 Nitrocellulose 0.9 Orthonitrotoluol 4.0 Woodmeal 2.5 Ammonium nitrate 62.8 Calcium sulphate (anhydrite) 2.0 Urea 2.0

The weight strength of the gelatine composition is 85.0 per cent of blasting gelatine.

Example 3 Parts 80:20 mixture of nitroglycerine and ethylene glycol dinitrate 25.5 Nitrocellulose 0.9 Orthonitrotoluol 4.0 Woodmeal 3.0 Ammonium nitrate 50.3 Sodium nitrate 12.0 Chalk 0.3 Urea 2.0 Calcium sulphate (anhydrite) 2.0

The weight strength of the gelatine composition is 78 per cent of blasting gelatine.

Example 4 Parts 80:20 mixture of nitroglycerine and ethylene glycol dinitrate 15.0 Nitrocellulose 0.3 Woodmeal 3.4 Ammonium nitrate 73.0 Aluminum 4.0 Chalk 0.3

Calcium sulphate (anhydrite) 4.0

The weight strength of the semi-gelatine composition is 82.9 per cent of blasting gelatine.

90 lb. charges of the compositions of Examples 1 to 4 when fired in a-tunnel give fumes which do not irritate the eyes or throat 15 minutes after firing. A charge of a similar composition to Examples 1 and 4 except that calcium sulphate is excluded, and charges of similar compositions to Examples 2 and 3 except that the urea and calcium sulphate are excluded, when fired in a tunnel give fumes which are highly irritant to the eyes or throat 15 minutes after firing.

A further advantage of the invention over the use of sulphur is that the use of sulphur necessitates the inclusion of at least 6 times its weight of sodium nitrate in order to prevent release of oxides of sulphur in the explosion gases whereas using calcium sulphate with or without urea as in the present invention it is unnecessary to include sodium nitrate, thus permitting the inclusion of an increased amount of ammonium nitrate into the explosive compositions to produce compositions of increased explosive power.

What we claim is:

1. High power gelatine and semi-gelatine blasting explosive compositions comprising nitrocellulose, at least 50% by weight of ammonium nitrate, at least 15% by weight of a liquid explosive nitric ester selected from the group consisting of nitroglycerine and ethylene glycol dinitrate, and 0.5% to 5% by weight of calcium sulphate.

2. High power gelatine and semi-gelatine blasting explosive compositions consisting essentially of nitrocellulose, at least 50% by weight of ammonium nitrate, at least 15% by weight of a liquid explosive nitric ester selected from the group consisting of nitroglycerine and ethylene glycol dinitrate, and 0.5% to 5% by weight of calcium sulphate.

3. High power gelatine and semi-gelatine blasting explosive compositions as claimed in claim 2 and including sodium nitrate.

4. High power gelatine and semi-gelatine blasting ex- 5 plosive compositions as claimed in claim 2 and including orthonitrotoluene.

5. High power gelatine and semi-gelatine blasting explosive compositions as claimed in claim 2 and including 0.5 to 5% by weight of urea.

6. High power gelatine and semi-gelatine blasting explosive compositions as claimed in claim 1 wherein 4 parts by weight of calcium sulphate is included in 100 parts by weight of explosive composition.

7. High power gelatine and semi-gelatine blasting ex- 15 plosive compositions as claimed in claim 1 wherein 100 parts by weight of explosive composition also include from 0.5 to 5 parts byweight of urea.

8. High power gelatine and semi-gelatine blasting explosive compositions as claimed in claim 7 which include 2 parts by weight of urea and 2 parts by weight of calcium sulphate per 100 parts by weight of explosive composition.

References Cited in the file of this patent vol. II, published (1943), by John Wiley & Sons, Inc., New York, and Chapman & Hall, Ltd., London, pages 352 and 353. (Copy in Division 70 (C Section).) 

1. HIGH POWER GELATINE AND SEMI-GELATINE BLASTING EXPLOSIVE COMPOSITIONS COMPRISING NITROCELLULOSE, AT LEAST 50% BY WEIGHT OF AMMONIUM NITRATE, AT LEAST 15% BY WEIGHT OF A LIQUID EXPLOSIVE NITRIC ESTER SELECTED FROM THE GROUP CONSISTING OF NITROGLYCERINE AND ETHYLENE GLYCOL DINITRATE, AND 0.5% TO 5% BY WEIGHT OF CALCIUM SULPHATE. 